Puppy Linux began life as a really cool small-sized Linux distribution designed primarily for lower specification hardware while still providing most of the amenities that make Linux fun and usable. It included lots of original utilities and tools for completing tasks and configurations without a lot of resource overhead.
Ubuntu just released the beta 1 version of their new LTS (Long Term Support) Distribution, Lucid 10.04. The theme is based on "light" and it looks great. Here's what to expect and what not to expect when you first install this new flavor of Ubuntu: